A phased array is a directive antenna made up of individual antennas or radiating patterns. The radiating pattern is determined by the amplitude and phase of the current at each element. The phased array antenna may have its beam electronically steered in angle by changing the phase of current at each element. A linear array consists of antenna elements arranged in a straight line in one dimension. A planar array is a two dimensional configuration of antenna elements arranged to lie in a plane. In both the linear and planar arrays, the element spacings are usually uniform. Further details of phrased array antenna are described in the book “Introduction to Radar Systems, 3d Edition”, by Merill I. Skolnik (McGraw-Hill, 2001).
An optical phased array is a phased array implemented in an optical device. One optical phased array has a single light source laser beam expanded through a lens into multiple beams, where each of the multiple beam passes through an array of phase shifters comprised of spatial light modulators (SLMs). The SLMs control the wavefront to shift the phase, such that each SLM may have a different phase delay, or relative time delays between the different SLMs, to control the steering of the beam and create a phase ramp. Further, changing the phase at each SLM in the array may also produce different antenna lob effects to provide a phased array antenna.